A disc brake has been hitherto employed as a braking device for a railway vehicle. As the disc brake, a railway wheel (hereinafter, also simply “wheel”) with brake discs (hereinafter, also simply “discs”) configured so that the discs are mounted on both side surfaces of the wheel respectively is frequently used.
If the wheel with discs is one configured so that the discs are fastened to the wheel simply by bolts, a heat load generated by the friction resulting from the sliding contact between each disc and a brake lining during braking is applied to the discs and the discs repeatedly thermally expand. This results in the center deviation of the discs relative to the wheel. This is noticeable in discs intended to meet the recent demand of higher speed and lighter weight. To prevent such center deviation of the discs, the development of a wheel with discs with center-deviation prevention keys included between the discs and the wheel is underway.
FIG. 1 is an exploded perspective view of a wheel with discs with center-deviation prevention keys included therein. The wheel with discs shown in FIG. 1 is configured to include a wheel 1, a pair of discs 2 each in the form of a doughnut disc, bolts 3 and nuts 4 for fastening these discs 2, and rod-like center-deviation prevention keys 5. A front surface of each of the paired discs 2 serves as a frictional surface, and a plurality of cooling fin portions 2a are formed radially on a rear surface of the disc 2. In FIG. 1, for the sake of convenience, the radial cooling fin portions 2a are simplified into and shown as one cooling fin portion 2a. 
Bolt holes 1b and 2b into which the bolts 3 are inserted are formed in a flat web 1a of the wheel 1 and the discs 2, respectively. Keyholes 1c into which the respective center-deviation prevention keys 5 are inserted are formed in the web 1a of the wheel 1, and key grooves 2c engaged with end portions of the respective center-deviation prevention keys 5 are formed in the rear surface of the discs 2 along a radial direction.
The paired discs 2 of the wheel with discs are arranged to face each other across the web 1a of the wheel 1, and the discs 2 are fastened to the wheel 1 by the bolts 3 inserted into the bolt holes 1b and 2b and the nuts 4 in a state in which the cooling fin portions 2a are in contact with the web 1a of the wheel 1. In this wheel with discs, the both end portions of the center-deviation prevention keys 5 are engaged with the key grooves 2c of the discs 2 while being inserted into the keyholes 1c of the wheel 1, and the center-deviation prevention keys 5 allow for the thermal expansion of the discs 2 with centers (center cores) of the discs 2 kept during braking.
While the number of bolts 3 is eight in FIG. 1, it suffices to use three or more bolts 3 so as to stably and securely fasten the discs 2 to the wheel 1. While the number of center-deviation prevention keys 5 is four, it suffices to use three or more center-deviation prevention keys 5 so that the center-deviation prevention keys 5 can fulfill their function.
The wheel with discs with the center-deviation prevention keys incorporated therein as described above has been hitherto assembled through procedures shown below.
(1) The bolts 3 are kept upright so as to correspond to positions of the bolt holes 1b and 2b formed in the wheel 1 and the discs 2. At this time, the bolts 3 are supported in upright profiles with heads thereof held by a dedicated bolt support tool.
(2) Out of the paired discs 2, the disc 2 arranged on a side opposite to a flange of the wheel 1 (hereinafter, also “opposite-to-flange disc 2”) is suspended by a crane, and moved downward with the front surface (frictional surface) thereof turned downward while carefully positioning the bolt holes 2b thereof with respect to the bolts 3. As a result, the opposite-to-flange disc 2 is made into a state in which the bolts 3 are inserted into the bolt holes 2b of the opposite-to-flange disc 2. Center cores (centers) of the bolt holes 2b of the opposite-to-flange disc 2 thereby match those of the bolts 3.(3) Next, the wheel 1 is suspended by the crane, and moved downward up to a state in which the wheel 1 slightly floats from the opposite-to-flange disc 2 with a surface of the wheel 1 opposite to the flange turned downward while carefully positioning the bolt holes 1b thereof with respect to the bolts 3. This makes the wheel 1 into a state in which the wheel 1 can fluctuate while remaining suspended within a range of a gap between the bolt holes 1b of the wheel 1 and the bolts 3 while the bolts 3 are being inserted into those bolt holes 1b. (4) While the wheel 1 is kept suspended by the crane, the keyholes 1c of the wheel 1 are positioned with respect to the key grooves 2c of the opposite-to-flange disk 2 and the center-deviation prevention keys 5 are inserted into the keyholes 1c. As a result, the center-deviation prevention keys 5 are inserted into the keyholes 1c of the wheel 1 with lower end portions thereof engaged with the key grooves 2c of the opposite-to-flange disc 2. Center cores (centers) of the bolt holes 1b of the wheel 1 and those of the bolt holes 2b of the opposite-to-flange disc 2 thereby match those of the bolts 3, and center cores of the keyholes 1c of the wheel 1 and those of the key grooves 2c of the opposite-to-flange disc 2 thereby match those of the center-deviation prevention keys 5, thus positioning the wheel 1 and the opposite-to-flange disc 2.(5) The wheel 1 is completely moved down. Thereafter, the disc 2 arranged on the same side as the flange of the wheel 1 (hereinafter, also “flange-side disc 2”) is suspended by the crane, and moved downward with the front surface (frictional surface) of the flange-side disc 2 turned upward while positioning the bolt holes 2b thereof with respect to the bolts 3 and positioning the key grooves 2c thereof with respect to the center-deviation prevention keys 5. As a result, the flange-side disc 2 is made into a state in which upper end portions of the core-deviation prevention keys 5 are engaged with the key grooves 2c of the flange-side disc 2 while the bolts 3 are being inserted into those bolt holes 2b of the flange-side disc 2. The center cores (centers) of the bolt holes 1b of the wheel 1 and those of the bolt holes 2b of the both discs 2 thereby match those of the bolts 3, and the center cores of the keyholes 1c of the wheel 1 and those of the key grooves 2c of the both discs 2 thereby match those of the center-deviation prevention keys 5, thus positioning the wheel 1 and the paired discs 2.(6) The nuts 4 are threaded into the bolts 3, thereby fastening the paired discs 2 to the wheel 1. Furthermore, the bolts 3 and the nuts 4 are additionally fastened to one another at a specified torque and thereby secured to one another.
In this way, the wheel with discs with the center-deviation prevention keys incorporated therein configured so that the paired discs 2 are arranged to face each other across the web 1a of the wheel 1 and the center-deviation prevention keys 5 penetrating this web 1a, and that the discs 2 are fastened to the wheel 1 by the bolts 3 is completed.
Meanwhile, at least three people are necessary if the wheel with discs is assembled as described above. This is because one person needs to operate the crane and two persons need to position the opposite-to-flange disc 2 suspended by the crane with respect to the bolts 3 in front and rear of the opposite-to-flange disc 2, respectively. Furthermore, it takes a long time because the assembly work for assembling the wheel with discs is performed entirely manually and the opposite-to-flange disc 2, in particular, should be positioned with respect to the bolts 3 extremely carefully. Owing to this, it is strongly desired to decrease the number of needed people and to shorten the assembly work time if the wheel with discs with the center-deviation prevention keys incorporated therein is to be assembled.
There is known the conventional technique for shortening the assembly work time for assembling the wheel with discs as follows. Patent Literature 1 discloses an assembling device that is intended at a wheel with discs that are fastened to the wheel simply by bolts, that is, a wheel with discs without center-deviation prevention keys and that is used if the wheel with discs is to be assembled.
The assembling device disclosed in Patent Literature 1 is configured as follows. A disc support for supporting inner diameters of the discs is fixedly arranged on a pedestal that can move up and down. Support of bolts to be inserted into bolt holes provided in the discs is disposed around this disc support. Moreover, a wheel support that penetrates the disc support and that is rotatable is installed at a concentric position within the disc support. The wheel support is configured to be movable upward and downward. With the assembling device configured as described above, the discs are assumed as those provided with inner diameter-side concave and convex portions, and notches are provided in the disc support to correspond to the inner diameter-side concave and convex portions. The inner diameter-side concave and convex portions of the opposite-to-flange disc are fitted first into the notches, thereby allowing centers of the bolt holes of the opposite-to-flange disc to match those of bolts of the support.
However, in a case of the wheel with discs with the center-deviation prevention keys incorporated therein to meet the recent demand of higher speed and lighter weight, concave and convex portions to be fitted into the notches of the disc supports are not provided near the inner diameter sides of the discs. It is, therefore, difficult for the assembling device disclosed in Patent Literature 1 to make the centers of the bolt holes of the opposite-to-flange disc match those of the bolts of the support. Provided that the centers of the bolt holes of the opposite-to-flange disc are made to match those of the bolts of the support, the opposite-to-flange disc suspended by a crane is moved downward while carefully positioning the bolt holes of the opposite-to-flange disc suspended by the crane with respect to the bolts of the support with at least three people involved similarly to the conventional manual work.
Therefore, the assembling device disclosed in Patent Literature 1 can insufficiently deal with the assembly work for assembling the wheel with discs with the center-deviation prevention keys incorporated therein.